The present invention relates generally to an alignment apparatus, and more particularly to an alignment apparatus for aligning with each other a wafer and a mask in an exposure apparatus. The present invention is suitable for an alignment apparatus used for an exposure apparatus that uses extreme ultraviolet (“EUV”) light as a light source for exposure.
Recent high performance and inexpensive electronic apparatuses need more economic and precisely manufactured semiconductors installed in them. Therefore, a high accuracy and efficiency manufacture are demand for an exposure apparatus that exposes a circuit pattern of the semiconductor. Then, the exposure apparatus includes an alignment apparatus that aligns with each other a mask and a wafer to execute high accuracy alignment and micro-fabrication.
The alignment apparatus reflects or transmits a light to a reference pattern formed on a mask, and the reflected light or transmitted light incident upon a slit support substrate that has a slit similar to the reference pattern. Moreover, the alignment apparatus detects the incident light to the slit by a photo-diode, and aligns with each other the mask and wafer based on the detection result. Recently, an EUV light is used as exposure light by a shorter wavelength of the exposure light.
However, the wavelength of the EUV light is one digit or more shorter than an ultraviolet light, and the slit support substrate that has high transmittance for the EUV light is not obtained.
A method of thinning the slit support substrate and a method of directly patterning to the photo-diode without using the slit support substrate are proposed as a method of solving this problem. See, for example, U.S. Pat. No. 6,130,431.
However, if the slit support substrate is thinned, a heat of the EUV light causes a distortion of the slit support substrate. In this case, a volume of the slit support substrate becomes small by thinning the slit support substrate, the heat quantity generated by absorbing the EUV light does not exhaust easily, the temperature rises, and the distortion is caused. Then, the distortion caused in the slit support substrate generates an alignment error, distortion and defocus error, and the detection accuracy is decreased. As a result, when the EUV light is used, a high accuracy alignment is difficult in the conventional alignment apparatus.
Moreover, the structure as U.S. Pat. No. 6,130,431 has a possibility to damage a surface of the photo-diode. As a result, when the EUV light is used, a high accuracy alignment is difficult in the conventional alignment apparatus.